CSL has continued the development of its Cardiac Scintillation Probe System begun in 1977. This non-imaging ECG-Gated scintillation probe, when used in conjunction with left ventricular (LV) catherization, permits simultaneous quantification of the variation of LV volume and pressure. By simultaneously measuring LV volume and LV pressure, parameters such as LV compliance can be continuously monitored. This year the previously implemented capability for real-time pressure-volume measurements were used to study the effect of verapermil on patients with asymmetric septal hypertrophy. It is anticipated that the quantitative pressure-volume relationships produced by the probe system will be able to better characterize the effects of the drug. Pressure-volume changes were analyzed to determine the best parameters for automatic calculation and presentation by the system and specific software was developed for this application. An additional detector to allow for simultaneous background and left ventrical volume measurements was added and this new capability is being evaluated. We are presently investigating the development of a small camera system which will combine the probe with a left ventricular image to ease probe placement and extend its application.